In brachytherapy, clinicians have utilized a physical grid having a standard pattern of apertures to guide needle insertion in connection with the placement of radioactive seeds within an anatomical organ of interest such as the prostate. Such a grid is also used for biopsies and other procedures. An example of such a grid is shown in FIG. 1. In FIG. 1, a square grid 102 includes a two-dimensional array of apertures 104, including first size apertures 106 and second size apertures 108, within a material 110. The apertures 104 are preformed and arranged equidistant from each other, center-to-center.
The illustrated grid 102 includes first graphical indicia (i.e., alphabetical characters, in this example) along the columns 114 and second graphical indicia (i.e., numbers, in this example) along the rows 116. The graphical indicia 114 and 116 provides a frame of reference, or a reference coordinate system (x,y) for each of the apertures 104. For example, the aperture 1041 corresponds to coordinates B,3. The procedure plan is created based on this coordinate system. The procedure plan, in general, indicates which apertures 104 will be used during the procedure, referencing the apertures 104 by their coordinates.
In FIG. 1, a closed line 118, which identifies a sub-region of grid 102 used for a particular procedure plan, is superimposed over the grid 102. The line 118 represents an outer perimeter 118 of the anatomical organ of interest. The outer perimeter 118 is determined, for example, by imaging a volume of the patient that includes the anatomical organ of interest, e.g., via CT or MR. The anatomical organ of interest is segmented from the volume. This may include drawing the line 118 via software drawings package. The segmented anatomical organ of interest is aligned with an image representing the grid 108. The outer perimeter 118 marking is transferred to the image representing the grid 102.
FIG. 2 (FIG. 3 in U.S. 2011/0009748 A1) shows use of such a grid in a procedure. Note that 104, 202 and 204 are not part of the original FIG. 3 in U.S. 2011/0009748 A1, but have been added to FIG. 2 for explanatory purposes.
In FIG. 2, an ultrasound probe 130 is supported by a housing 128, and a grid 115 is supported by a connecting arm 126 to the housing 128. The grid 115 is similar to that of 102 in FIG. 1 in that it includes a standard pattern of apertures 104. The ultrasound probe 130 is shown partially inserted into the rectum 3 of the patient. A clinician 200, based on coordinates for an aperture 104 from the procedure plan, inserts a needle 50 through the aperture 104 and guides the needle 50 to the anatomical organ of interest 2, using an ultrasound image generated with data acquired by the ultrasound probe 130 to guide the needle 50 to an area of interest within the anatomical organ of interest 2.
Unfortunately, the areas of interest are limited by the standard pattern of the apertures 104 of the grid 115 to only the areas reachable through the apertures 104. For example, in FIG. 2, areas 202 are reachable through the apertures 104. However, where there is no aperture between the two shown apertures 104, an area 204 between the areas 202 is not reachable by the needle 50. As such, areas of interest to a clinician may not be reachable when using the grid 115 and, thus, the areas accessible utilizing the grid 115 for a particular procedure may not be the areas of interest to the clinician. Furthermore, the clinician may have to keep a mental note of which apertures have already been used so as not to use the same aperture twice and repeat an already completed step of the plan.